In integrated circuit (IC) manufacturing, semiconductor devices such as the transistors are fabricated on a silicon substrate and then connected together to perform the desired circuit functions. This connection process is generally called “metallization”, and can be performed using a number of photolithographic patterning, etching, and deposition steps.
To form the connections, metallization layers include vias and interconnect structures that function as electrical pathways to interconnect the semiconductor devices. In the metallization layers, the interconnect structures and vias form a contact with the substrate to form a metal-semiconductor contact. However, direct metal to semiconductor contact may be highly resistive. As devices scale smaller and smaller, such resistivity can be highly undesirable.